The present invention is directed to new and useful improvements in electric dry shavers and in particular to a cutter head assembly for a foil type electric dry shaver.
Electric dry shavers of the type generally referred to as foil type electric dry shavers are well-known. The latter type electric dry shaver differs from other shavers which utilize stationary outer cutters and movable inner cutters in that the outer cutter element is comprised of a resilient, flexible metallic foil member. The inner cutter for these shavers usually includes arcuate shaped blades in shearing contact with the undersurface of the outer cutter foil member. The foil member is provided with a plurality of hair reception slots through which hair bristles are fed during the act of shaving for shearing by the movable inner cutter. The foil member is of generally rectangular configuration prior to mounting on the shaver casing and is made of nickel and formed by an electroforming process. Spaced marginal portions of the foil are usually secured to the walls or other portions of the shaver casing and when the foil is mounted on the casing the intermediate portion is bowed about the arcuate inner cutter blades conforming the foil to the configuration thereof.
The arcuate shaped inner cutter is mounted on a support member and urged into shearing engagement with the undersurface of the foil by spring means mounted within the casing. It has been found that the arcuate shape of the foil and mating configuration of the inner cutter blades allows for a more efficient presentation of the hair reception slots in the foil to receive hair bristles. In some foil type shavers therefore the foil is shaped into two or more parallel arcuate rows providing a multiple bowed or curved outer cutter head surface. To accommodate these multiple outer cutting rows the inner cutter is provided with a like number of rows of spaced arcuate shaped blades mounted on a support member and placed into cutting cooperation with the foil for reciprocating movement relative to the undersurface of the foil.
In use, these multiple bowed cutting surfaces have proven quite desirable in providing more usable shaving area and a multiple combing and cutting action. Various problems however, are encountered in the manufacture and use thereof. In some instances, proper balancing of the driven mass of the inner cutter is hampered by the undesired spacing between the rows of inner cutter blades which causes the assembly either to move laterally in reciprocation in the longitudinal direction of the outer cutter foil, or to vibrate in use. In other instances, the relatively large inner cutter structure results in undesired spacing between the arcuate undersurfaces of the foil and the inner cutter resulting in a lack of contact between the inner cutter blades and the foil and a resulting loss of cutting action. The undesirable size of the inner cutter assembly also increases the area of operation thereof within the shaver and presents problems in providing an effective drive connection with the cutter drive means. In addition the greater the radius of the arcuate inner cutter blade the more difficult the problems are in assuring proper contact between the edges thereof and the undersurface of the outer cutter foil in a multiple bowed cutter head assembly.
Further, while the foil shavers are satisfactory for close shaving of short hair bristles, long hairs tend to bend over and lie close against the skin instead of entering the openings in the foil. If the foil member is formed with openings large enough to comb and accept long hairs the skin of the user will tend to enter the cutter assembly and come in contact with the moving cutter blades causing irritation. To overcome the foregoing difficulty some foil type shavers are provided with a trimmer unit having comb-like cutting teeth mounted adjacent the outer cutter foil to cut long hairs in advance thereof and to feed the shortend bristles thereof to the small apertures of the foil member. Such a trimmer unit is disclosed in a co-pending patent application SER. No. 648,056 filed Jan. 12, 1976.
In foil shavers having the aforementioned multiple outer cutter rows it has been found desirable to have the cutter mass located between the rows of arcuate cutter blades for connection of the inner cutter support member with the motor drive arm. In prior art cutter assemblies, the lateral spacing between the arcuate rows of inner cutter blades results in balancing problems and ensuing vibrations in operation of the inner cutter. In response to these aforementioned problems the overall size of the cutter assembly has been increased in prior art shavers resulting in enlarged areas of operation within the limited spacial confines of the relatively small shaver casing. As a result difficulties have been encountered in providing a foil type shaver having a multiple bowed foil outer cutter either alone or in combination with the desirable trimmer and long hair cutter unit.
IN addition to the mentioned pending patent application other prior art patents which disclose electric shavers which are typical of those discussed are U.S. Pat. Nos. 3,376,642; 3,561,118; 3,634,936; 3,742,072 and 3,874,079 and German Pat. Nos. 932,172 and 1,022,121.
It is an object of the present invention to provide a novel cutter head assembly and shaving system for an electric dry shaver.
Another object is to provide a novel cutter head assembly for a foil type shaver having multiple arcuate or bowed shaped outer cutter surfaces wherein the inner cutter assembly is maintained in close shearing contact with the undersurface of the foil.
A further object is to provide a novel compact cutter head assembly providing increased cutting efficiency within the limited spatial confines of an electric dry shaver casing.
Another object is to provide a novel inner cutter assembly for a foil type electric dry shaver having novel means for balancing the inner cutter assembly in operation.
A still further object is to provide a novel balanced inner cutter assembly for a foil type shaver having a more efficient cutting action and means for feeding hair bristles for the cutting system.